1. Field of the Invention
The present invention relates to an implantable heart monitoring device of the type having a control circuit connected to one or more sensors suited to be positioned in or at the heart of a living being, at least a first of the sensors being positionable in the coronary sinus region of the heart and arranged to sense at least one constituent of blood, and wherein the control circuit receives signals from the first sensor, which are related to the blood constituent, and wherein the control circuit senses the activity of the heart, via signals from one or more of the sensors, such that events signifying a heart cycle are detectable by the control circuit. The invention also relates to a heart monitoring system including such a heart monitoring device and a method for monitoring a heart.
2. Description of the Prior Art
Many different devices for monitoring the performance of a heart are known. Often these devices are also able to deliver stimulation pulses to the heart. The devices are often able to sense the electrical activity in the heart. It is also known to sense other physiological parameters, such as pressure, oxygen level, pH, nitric oxide, carbon dioxide, etc.
U.S. Pat. No. 5,213,098 discloses a cardiac stimulator with an oxygen saturation sensor positioned in the coronary sinus of the heart. The device is also able to sense the blood pressure and the electrical activity of the heart. The stimulator may be used to control the atrial stimulation in order to improve the filling of the ventricles.
U.S. Pat. No. 5,199,428 discloses a device for detecting myocardial ischemia. A pH sensor or an oxygen saturation sensor may be positioned in the coronary sinus. The device can be used to stimulate for example the left and/or right carotid sinus nerves in order to decrease cardiac workload.
U.S. Pat. No. 6,236,873 discloses an electrochemical sensor for measuring the oxygen content in blood.
U.S. Pat. No. 4,202,339 describes a sensor for measuring the oxygen saturation level in blood.
U.S. Pat. No. 4,453,537 discloses a device for sensing, inter alia, the carbon dioxide content in the blood.
U.S. Pat. No. 5,582,170 discloses a fiber optic sensor for sensing the nitric oxide content in blood.
U.S. Pat. No. 5,720,768 discloses different possible electrode positions in order to stimulate or sense the different chambers of the heart.
U.S. Pat. No. 6,070,100 discloses that electrodes may be positioned in both the left and the right atrium as well as in or at the left and the right ventricles. The document describes the possibility of sensing the impedance between different electrodes. The sensed impedance values may be used to improve the cardiac output.
U.S. Pat. No. 5,156,147 discloses a pacemaker which has a hemodynamic sensor which is arranged to provide a signal representing the pumping performance of the heart. The hemodynamic sensor may be a piezoelectric pressure sensor.